diff --git a/vllm/entrypoints/pooling/base/io_processor.py b/vllm/entrypoints/pooling/base/io_processor.py
index 05ec69e44a..0d9431f022 100644
--- a/vllm/entrypoints/pooling/base/io_processor.py
+++ b/vllm/entrypoints/pooling/base/io_processor.py
@@ -207,7 +207,10 @@ class PoolingIOProcessor:
         else:
             pooling_params = ctx.pooling_params
 
-        params_seq = self._params_to_seq(pooling_params, num_requests)
+        # Clone to avoid modifying the caller's pooling parameters.
+        params_seq = [
+            param.clone() for param in self._params_to_seq(pooling_params, num_requests)
+        ]
 
         for param in params_seq:
             if param.task is None:
diff --git a/vllm/entrypoints/pooling/pooling/io_processor.py b/vllm/entrypoints/pooling/pooling/io_processor.py
index 4b18cfc9e1..d5132f2a66 100644
--- a/vllm/entrypoints/pooling/pooling/io_processor.py
+++ b/vllm/entrypoints/pooling/pooling/io_processor.py
@@ -168,7 +168,7 @@ class PluginWithIOProcessorPlugins(PoolingIOProcessor):
             pooling_params = ctx.pooling_params
 
         params_seq: list[PoolingParams] = [
-            self.io_processor.merge_pooling_params(param)
+            self.io_processor.merge_pooling_params(param.clone())
             for param in self._params_to_seq(
                 pooling_params,
                 num_requests,